1. Field of the Invention
The present invention relates generally to a method for manufacturing surface gratings on lasers having a stepped or mesa structure.
2. Description of the Prior Art
A distributed feedback-metal cladded ridge waveguide laser (DFB-MCRW laser) is disclosed in U.S. patent application Ser. No. 785,228 filed on Oct. 7, 1985. The strip waveguide laser includes a grating structure formed by single step epitaxy along the strip, or ridge, and along the lateral regions on either side thereof as well. It is necessary in order to realize a DFB-MCRW laser in single step epitaxy to produce gratings in the more deeply situated regions immediately adjacent the elevated region of the mesa structure. It is possible to produce such surface gratings in the more deeply situated regions by using methods of multi-layer masking. However, problems arise in that the photo-resist cannot be whirled into substrates having mesa structures.